java - JAXB - 如何以两种方式解析元素

Question

我正在尝试解析一个具有与其他类的多个双向连接的类。为了防止无限循环问题和其他原因，我想以自定义方式解析一些属性。

即我有类 MovieImpl (实现电影接口(interface))，其中包含 Actor 列表 (PersonImpl) 和导演的一个字段 (PersonImpl)(当然还有其他字段):

@XmlRootElement
@XmlSeeAlso({ PersonImpl.class })
@Entity
public class MovieImpl implements Movie {

    @Id
    @Column(name = "movieId", unique = true)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    int _id;

    ...

    @ManyToOne(fetch = FetchType.LAZY, targetEntity = PersonImpl.class)
    @JoinColumn(name = "directorId")
    Person _director;

    ...

    @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, targetEntity = PersonImpl.class)
    @JoinTable(name = "movie_has_actors", joinColumns = { @JoinColumn(name = "movieId", nullable = false) }, inverseJoinColumns = { @JoinColumn(name = "personId", nullable = false) })
    Collection<Person> _actors;

    ...
}

我的 PersonImpl 类有一个电影列表:

@XmlRootElement
@XmlSeeAlso({ MovieImpl.class })
@Entity
public class PersonImpl implements Person {

    ...
    private int _id;
    private String _name;

    @ManyToMany(mappedBy = "_actors", targetEntity = MovieImpl.class)
    private Collection<Movie> _movies;

    ...

}

那么，jaxb 有没有一种方法可以在从电影对象渲染 Actor 时仅显示 Actor 的姓名和 id。另一方面:当电影从人物对象渲染时，只显示电影中的一些其他字段？

即:

<movie>
    <id>82303482</id>
    ...
    <director>
        <id>340980</id>
        <name>xyz</name>
    </director>
    <actors>
        <actor>
            <id>479834</id>
            <name>xyz</name>
        </actor>
        <actor>
            <id>3434234</id>
            <name>abc</name>
        </actor>
    ...
</movie>


<actor>
    <id>34843</id>
    <name>abc</name>
    ...
    <movies>
        <movie>
            <id>3489</id>
            <title>asdf</title>
            ...
        </movie>
        <movie>
            <id>4534534</id>
            <title>qwer</title>
            ...
        </movie>
    </movies>
</actor>

感谢您提前提供帮助。

更新:当我将 @XmlInverseReference 注释添加到字段时，它只给我类似的内容:

...
<_actors>
    com.company.package...PersonImpl@2450c3
</_actors>
<_actors>
    com.company.package...PersonImpl@4e98166
</_actors>
<actors>
    com.company.package...PersonImpl@2450c3
</actors>
<actors>
    com.company.package...PersonImpl@4e98166
</actors>
...

1. 为什么有 2 个来自 actor 的字段(_actor 和 actor)？
2. 为什么 Actor 的字段没有显示？

Answer 1

由于根据您的问题标签，您正在使用 MOXy:

MOXy 允许通过 @XmlInverseReference 扩展进行双向映射(您需要使用 EclipseLink 2.5.0 或更高版本才能在两个方向上写入关系):

• http://blog.bdoughan.com/2013/03/moxys-xmlinversereference-is-now-truly.html

MOXy 还允许您使用对象图扩展来编码数据子集:

• http://blog.bdoughan.com/2013/03/moxys-object-graphs-inputoutput-partial.html

<小时/>

注意

下面是答案应该是什么，但是 @XmlElementWrapper 和 @XmlInverseReference 似乎存在编码错误。

Java 模型

MovieImpl

import java.util.Collection;
import javax.persistence.*;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.*;

@XmlRootElement(name="movie")
@XmlAccessorType(XmlAccessType.FIELD)
@XmlNamedObjectGraph(
        name="partial",
        attributeNodes={
            @XmlNamedAttributeNode("_id"),
            @XmlNamedAttributeNode(value="_director", subgraph="partial"),
            @XmlNamedAttributeNode(value="_actors", subgraph="partial")
        },
        subgraphs={
            @XmlNamedSubgraph(
                name="location",
                attributeNodes = {
                    @XmlNamedAttributeNode("_id"),
                    @XmlNamedAttributeNode("_name")
                }
            )
        }
    )
@Entity
public class MovieImpl implements Movie {

    @XmlElement(name="id")
    @Id
    @Column(name = "movieId", unique = true)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    int _id;

    @XmlElement(name="director", type=PersonImpl.class)
    @ManyToOne(fetch = FetchType.LAZY, targetEntity = PersonImpl.class)
    @JoinColumn(name = "directorId")
    Person _director;

    @XmlElementWrapper(name="actors")
    @XmlElement(name="actor", type=PersonImpl.class)
    @XmlInverseReference(mappedBy="_actors")
    @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, targetEntity = PersonImpl.class)
    @JoinTable(name = "movie_has_actors", joinColumns = { @JoinColumn(name = "movieId", nullable = false) }, inverseJoinColumns = { @JoinColumn(name = "personId", nullable = false) })
    Collection<Person> _actors;

    public Collection<Person> getActors() {
        return _actors;
    }

}

PersonImpl

import java.util.Collection;
import javax.persistence.*;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.*;

@XmlRootElement(name="actor")
@XmlAccessorType(XmlAccessType.FIELD)
@XmlNamedObjectGraph(
        name="partial",
        attributeNodes={
            @XmlNamedAttributeNode("_id"),
            @XmlNamedAttributeNode("_name"),
            @XmlNamedAttributeNode(value="_movies", subgraph="partial")
        },
        subgraphs={
            @XmlNamedSubgraph(
                name="location",
                attributeNodes = {
                    @XmlNamedAttributeNode("_id"),
                    @XmlNamedAttributeNode("_name")
                }
            )
        }
    )
@Entity
public class PersonImpl implements Person {

    @XmlElement(name="id")
    private int _id;

    @XmlElement(name="name")
    private String _name;

    @XmlElementWrapper(name="movies")
    @XmlElement(name="movie", type=MovieImpl.class)
    @XmlInverseReference(mappedBy="_actors")
    @ManyToMany(mappedBy = "_actors", targetEntity = MovieImpl.class)
    private Collection<Movie> _movies;

}

演示代码

演示

import java.io.File;
import javax.xml.bind.*;
import org.eclipse.persistence.jaxb.MarshallerProperties;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(MovieImpl.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum21764131/input.xml");
        Movie movie = (Movie) unmarshaller.unmarshal(xml);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty(MarshallerProperties.OBJECT_GRAPH, "partial");
        marshaller.marshal(movie.getActors().toArray()[0], System.out);
    }

}